Trunk hunting circuit



c. G. SPENC R 2 295,181

TRUNK HUNTING CIRCUIT Filed Sept. 24, 1941 Sept. 8, 1942.

POLARIZED I /os'-E:]

INVENTOR e. 6. SPA-Nam ATTORNEY Patented Sept. 8, 1942 UNITED STTES PAT 'i QFFlCE 2,295,187 TRUNK HUNTING CIRCUIT Charles G. Spencer, East Orange, to Bell Telephone Laboratories, New Yerk, N. Y., a corporation of N. J., assignor Incorporated,

New York Application September 24, 1941, Serial No. 412,059 6 Claims. (01. 17918) This invention relates to telephone systems and has for its object to increase the speed of operation of hunting switches.

Heretofore, in

412,073, filed September 24, 1941.

Wiper I00 is the test wiper of a switch having access to a plurality of outgoing circuits, for example, operators positions. Busy positions are marked by ground as indicated at positions are marked by battery through a reeither battery or ground.

However, it is possible that, due of a number of unstandard conditions, the cirwiper I00, for

may be opened. of the circuit for huntis operated, followed by relay I04. With relay circuit is closed from battery through the Winding of stepping magnet I06 and its back contact, winding of polarized 55 operate.

test relay I01, contact of relay I04, to test wiper I00. At the same time a circuit is closed from ground over the contact of relay I05, high resistance left winding of relay I08 to the winding of relay I01 in parallel with magnet I 06. Magnet I06 cannot operate in series with the high as above described.

If, while hunting for an idle position, wiper I00 encounters a terminal having an open circuit as at I03, neither relay I01 nor magnet I06 can Under this condition a circuit exists operate in series with the high resistance winding of relay I08, as above mentioned, but relay thereto operates magnet I06 relay I08 causing that relay to release. If, further, this terminal is also connected'to an open circuit, relay I 08 reoperates and magnet I06 also reoperates to again advance test wiper I00.

What is claimed is:

1. In a telephone system, a switch, a magnet for causing said switch to advance in search of an idle trunk, a polarized relay, a test wiper for said switch, a first operating circuit for said magnet including said polarized relay and said test wiper in series, means in busy trunks for operating said magnet over said first circuit, means in idle trunks for operating said relay, a second circuit for said magnet and means to closed said second circuit when said test wiper rests on a trunk which does not complete said first circuit.

2. In a telephone system, a switch, a magnet for causing said switch to advance in search of an idle trunk, a polarized relay, a test wiper for said switch, an operating circuit for said magnet including said polarized relay and said test wiper in series, means in busy trunks for operating said magnet over said circuit, means in idle trunks for operating said relay, a second circuit for said magnet, means to close said second circuit when said test wiper rests on a trunk which doesnot complete said first circuit and means under the control of said polarized relay for preventing the operation of said magnet in said second circuit.

3. In a telephone system, a switch, a magnet for causing said switch to advance in search of an idle trunk, a polarized relay, a test wiper for said switch, an operating circuit for said magnet including said polarized relay and said test wiper in series, means in busy trunks for operating said magnet over said circuit, means in idle trunks for operating said relay, an auxiliary circuit for said magnet, and means under the control of said polarized relay to render said auxiliary circuit inefiective.

4. In a telephone system, a switch, a magnet for causing said switch to advance in search of an idle trunk, a polarized relay, a test wiper for said switch, an operating circuit for said magnet including said polarized relay and said test wiper in series, means in busy trunks for operating vent the operation of said magnet over said circuit, means in idle trunks for operating said relay, a high resistance, normally ineffective, auxiliary circuit for said magnet, and means effective when said test wiper rests on a trunk which does not complete said operating circuit, to reduce the resistance in said auxiliary circuit to permit said magnet to operate.

5. In a telephone system, a switch, a magnet for causing said switch to advance in search of an idle trunk, a polarized relay, a test wiper for said switch, an operating circuit for said magnet including said polarized relay and said test wiper in series, means in busy trunks for operating said magnet over said circuit, means in idle trunks for operating said relay, a second circuit for said magnet exclusive of said polarized relay, means to close said second circuit when said test wiper rests on a trunk which does not complete said first circuit and means under the control of said polarized relay for preventing the closure of said second circuit.

6. In a telephone system, a switch, a magnet for causing said switch to advance in search of an idle trunk, a polarized relay, a test wiper for said switch, an operating circuit for said magnet including said polarized relay and said test wiper in series, means in busy trunks for operating said magnet over said circuit, means in idle trunks for operating said polarized relay, an auxiliary relay having a high resistance winding and a low resistance winding, a secondary circuit for said magnet including said high resistance winding, said auxiliary relay when operated connecting its low resistance winding in parallel with its high resistance winding to provide a low resistance circuit in which said magnet can operate, means controlled by said magnet to prevent the operation of said auxiliary relay and means controlled by said polarized relay to presaid auxiliary relay from being effective to close said low resistance circuit.

CHARLES G. SPENCER. 

